1. Field of the Invention
The present invention relates to an image processing apparatus and method which can provide an image allowing easy comprehension of a curved cross-sectional shape of a target under observation.
2. Description of the Related Art
Image processing apparatuses recently used in the field of medical images are widely used in many hospitals, examination organizations, and the like in combination with ultrasound diagnostic apparatuses, X-ray CT scanners, magnetic resonance imaging apparatuses, and the like. This image processing apparatus can provide various kinds of images useful as clinical information along with increases in image processing speed and resolution, and is used, for example, for imaging of an alimentary tract lumen which is performed to check blood vessel running, an alimentary tract tumor, the formation of a plaque (blood clot), stenochoria, and the like in a simulation or the like before a surgical operation.
In such an image processing apparatus, as a conventional method of displaying a cross-section of a target in a manner easy to understand on the basis of a three-dimensional image including a curved observation target, a technique called curved multi-planar reformatting (Curved MPR: to be abbreviated as “C-MPR”) is known. For example, an image is formed by C-MPR according to the following sequence: (1) setting polygonal lines on the screen on which an overall three-dimensional image is displayed, (2) forming a cross-section (C-MPR cross-section) containing the polygonal lines set perpendicular to the screen, and (3) displaying pixel values on the cross-section as a two-dimensional image.
FIG. 6 is a view for explaining a C-MPR image (an image generated by C-MPR). Referring to FIG. 6, polygonal lines a, b, c, and d which define a C-MPR cross-section are formed by four straight lines. A C-MPR image is generated by displaying pixel values on the C-MPR cross-section comprising four planes which include the respective polygonal lines and are perpendicular to the screen without any change. That is, C-MPR is a method of displaying pixel values side by side on one plane, which are not present on a plane as a whole. According to this technique, images on a curved surface comprising planes can be observed at once.
Another method of displaying pixels values side by side on one plane, which are not present on a plane as a whole, is known. For example, this method is executed according to the following sequence: (1) setting polygonal lines on the screen on which an overall three-dimensional image is displayed, (2) forming a cross-section (C-PC cross-section) containing the polygonal lines set perpendicular to the screen, and (3) displaying only pixel values on the cross-section by projecting them on a projection surface in consideration of a line of sight. In this case, this display method will be referred to as curved plane cut (C-PC).
FIG. 7 is a view for explaining a C-PC image. Referring to FIG. 7, the right-side portion indicates a C-PC image, which is displayed to show the shape of a C-PC cross-section. An overall C-PC cross-section can be observed at different lines of sight upon rotation.